Acute exposure of cerebral arteries to alcohol (as in binge drinking) is known to cause cerebral vasospasm and stroke. The risk for this pathology is increased by mechanisms that impair cerebral vasodilation, such as high cholesterol Most of the evidence indicates that alcohol-induced cerebral artery constriction is due to a direct contraction of cerebral smooth muscle by ethanol (EtOH). However, the ionic mechanisms that determine EtOH-induced cerebrovascular contraction are unknown. Large conductance, Ca++-activated K + (BK) channel activity in the cerebral artery smooth muscle critically limits the degree of contraction. BK channels consist of alpha (encoded by the slo gene) and beta subunits. Slo expression renders currents that bear all the key features of BK channels. The ultimate goal of this application is to identify the molecular factors and mechanisms determining EtOH modulation of cerebrovascular BK channel activity and the contribution of this modulation to cerebrovascular smooth muscle contraction induced by acute EtOH. Based on our previous data, we have narrowed down the molecular entities determining a particular BK channel response to acute EtOH exposure to: 1) the particular slo channel isoform; and 2) the lipid (in particular, steroid) environment of the slo subunit. Therefore, using a combination of pharmacological, electrophysiological (patch-clamp) and Molecular Biology techniques, here we will comprehensively address EtOH modulation of BK channel function in cerebrovascular smooth muscle by sequentially examining drug action in: 1) the isolated cerebral artery to determine the contribution of EtOH modulation of BK channel function to alcohol action on cerebral artery constriction; 2) isolated cerebrovascular myocytes to address a direct EtOH-BK channel complex interaction when the channel is embedded in its natural membrane environment and, taken advantage of our recent cloning of slo from cerebral artery myocytes, 3) model systems to probe a direct slo subunit-EtOH interaction and establish its molecular determinants, including modulation by membrane steroids. Pinpointing the molecular mechanisms involved in EtOH action on cerebrovascular BK channels will bring fundamental information for the rationale design of drugs of potential therapeutic use in alcohol-induced cerebrovascular disease.